MID INFRARED IMAGING OF ULTRA COMPACT HII REGIONS/ CO CLUMPS

as a part of detailed study of galactic star forming regions, we plan to complement farinfrared, submillimeter, and radio continuum measurements with iso observations in the midinfrared. the main purpose is to obtain high angular resolution maps in appropriate filters (in the 312 microns region) centered at wavelengths corresponding to the pah features and their nearby continuua. the isocam data will give important clues to the understanding of: (1) distribution of dust grains r^ant for transient heating; and (2) role of small grains vis a vis normal large grains (the latter responsible for the farinfrared emission). combining the results of radio continuum, farir and midir can constrain detailed radiation transfer model parameters leading to the determination of dust properties and dust distribution etc. we propose high angular resolution near/midinfrared imaging of three ultra compact hii regions / co clumps. these are not planned to be observed by the iso, either under guaranteed time or guest observer programmes. the transiras band farinfrared observations of these objects in two bands centered at 130 and 170 micron with angular resolution of about 1. have already been made using the tata institute.s (tifr) 100 cm balloonborne telescope. the hires processed iras maps of these sources have also been obtained in all the four bands. some of these objects show multiple structures in the tifr farinfrared maps. the iso provides an unique opportunity to get high angular resolution maps of these sources at astrophysically important wavelengths (centered at pah features etc). we plan to observe these sources in 7 filters of isocam, 4 of which (3.3, 6, 7.75 and 11.4 micron) cover pah bands and the rest 3, neighbouring wavelengths for comparison. as all the target sources are quite strong, a very nominal observation time suffices for this proposal. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]